1. Field of the Invention
The present invention relates to a head array unit, an image forming apparatus and a head replacing method.
2. Description of the Related Art
As a printer, a facsimile apparatus, a copier, a plotter or a multifunction peripheral (MFP) that has functions as a printer, a facsimile, a copier and/or a plotter, for example, an image forming apparatus in a liquid discharging recording type (ink-jet recording apparatus) which uses a recording head that discharges ink droplets is known. The image forming apparatus in the liquid discharging recording type is such that ink droplets are discharged by a recording head to paper that is conveyed and forming an image is carried out. “Paper” is not particularly limited to paper, includes an OHP (i.e., overhead projector) film (i.e., a transparency film which may be suitably used in an overhead projector) or such, means one to which ink droplets or other liquid droplets can adhere, and may also be referred to as a to-be-recorded medium or a recording medium, recording paper, or such. The forming an image has the same meaning as recording, printing or such, hereinafter. The image forming apparatus in the liquid discharging recording type includes a serial-type image forming apparatus and a line-type image forming apparatus. The serial-type image forming apparatus is such that a recording head discharges liquid droplets while moving in a main scan direction and forms an image. The line-type image forming apparatus is such that a line-type head that discharges liquid droplets in a condition of not moving and forms an image is used.
Further, hereinafter, an image forming apparatus in a liquid discharging recording type means an apparatus that discharges liquid to a medium such as paper, thread, fibers, textile, leather, metal, plastic, glass, wood, ceramics or such, and carries out forming an image. Further, “forming an image” means not only giving an image having a meaning, such as letters, figures or such, to the medium, but also giving an image having no meaning, such as patterns, to the medium (i.e., merely landing liquid droplets on the medium). Further, “liquid” to be discharged is not limited to ink, is not particularly limited as long as it becomes liquid when it is discharged, and, for example, may include a DNA sample, resist, pattern material or such. Further, “image” is not limited to a two-dimensional image, but may also include an image that is given to a three-dimensionally formed medium or a figure obtained as a result of a solid body itself being three-dimensionally shaped.
As a full-line head used in the line-type image forming apparatus, which head has a length of a nozzle row corresponding to a width of a recording medium such as paper or a long-size head having a length of a nozzle row corresponding to a half of the width of the recording medium (hereinafter both heads may be generally referred to as a “long-size head”), a configuration (referred to as a head array unit) is known in which plural short-size heads are arranged (to form an array) along a direction of the width of the recording medium.
In a case where plural heads are mounted on a head supporting member and the head array unit is formed, it may be difficult for a user to replace the heads if the heads are fixed directly to the head supporting member.
In this regard, a configuration is known in which heads and spacer members are put and fixed together, and the spacer members are fixed to a head supporting member (base member) detachably (see Japanese Laid-Open Patent Applications Nos. 2006-264181 and 2008-179081).
In the above-mentioned configuration in which the heads (head units) and the spacer members are put and fixed together and the spacer members are fixed to the head supporting member (base member) detachably, convenience is improved in replacement work (removing and loading work). However, when the heads are replaced with other heads, it is necessary to newly position the spacer members with respect to the head supporting member. Therefore, when including the positioning work, convenience in head replacement work may not be so improved.
Further, in a case where positioning parts are formed directly on a head supporting member, all of the positions of many heads arranged are to be positioned with high accuracy, and therefore, materials and a processing method for processing the head supporting member are limited, and thus, the head supporting member may become very expensive.